1. Field of the Invention
The invention relates to actuators, and more particularly, to actuators for an electromagnetically adjustable valve.
2. Description of the Related Art
An actuator for an electromagnetically adjustable valve is known, for example, from DE 41 37 821 A1. The actuator comprises a coil which exerts a magnetic force on an armature as an adjustment element for a valve. Actuators are frequently composed of a plurality of individual components whose individual tolerances influence the operating behavior of the actuator. In an electromagnetic actuator, the usable operating travel distance of the adjustment element and the effective force are significant and essential operating parameters. In order to more precisely enable compliance with these influencing variables, the adjustment element in DE 41 37 821 A1 is of a design which is divided into two assemblies and provided with an adjustment device. The adjustment device is composed of a threaded connection between the two assemblies of the adjustment element. The adjustment device can be used to set the entire length of the adjustment element to a defined dimension. The defined longitudinal dimension is in a ratio to the central housing orifice of the actuator which is covered by a closure screw which has sealing rings for sealing the housing orifice. The end-side distance between the closure screw and the rear of the adjustment element determines the maximum stroke of the adjustment element. The setting of the adjustment screw is defined by the necessary level of prestressing of the sealing rings. Consequently, for a longitudinal dimension X for the adjustment element to be set correctly, the operating stroke is determined taking into account the tolerances of the depth of the housing orifice and the screw-in length of the closure screw. The possible tolerance influences have indeed been reduced, but the effect of the tolerances can still be measured.
This type of adjustment device requires an additional protection of the setting length of the adjustment element, for example by means of a thread paste. Otherwise, the possibility of the length setting not being adjusted while the actuator is operating or during the setting of the spring prestress of the springs within the adjustment element is not excluded. The size of the components must also be taken into consideration. The real size of the individual components is significantly smaller so that the threaded connection is significantly weaker than presumed, with the operating pressure in the throughflow duct (reference numeral 8) acting on the threaded connection.